The present invention relates to a method and an apparatus for separating a composite member such as a bonded substrate stack, a thin film manufacturing method, a method and an apparatus for detecting a feature portion of a composite member, and a composite member processing apparatus.
A substrate (SOI substrate) having an SOI (Silicon On Insulator) structure is known as a substrate having a single-crystal Si layer on an insulating layer. A device using this SOI substrate has many advantages that cannot be achieved by ordinary Si substrates. Examples of the advantages are as follows.
(1) The integration degree can be increased because dielectric isolation is easy.
(2) The radiation resistance can be increased.
(3) The operating speed of the device can be increased because the stray capacitance is small.
(4) No well step is necessary.
(5) Latch-up can be prevented.
(6) A complete depletion type field effect transistor can be formed by thin film formation.
Since an SOI structure has the above various advantages, researches have been made on its formation method for several decades.
As a method, an SOI structure is formed by bonding a single-crystal Si substrate to another thermally oxidized single-crystal Si substrate by annealing or an adhesive. In this method, an active layer for forming a device must be uniformly thin. More specifically, a single-crystal Si substrate having a thickness of several hundred microns must be thinned down to the micron order or less.
To thin the substrate, polishing or selective etching can be used.
A single-crystal Si substrate can hardly be uniformly thinned by polishing. Especially, in thinning to the submicron order, the variation range is several tens of percent. As the wafer size becomes large, this difficulty becomes more pronounced.
Selective etching is effective to uniformly thin the substrate. However, the selectivity ratio is as low as about 102, the surface planarity after etching is poor, and the crystallinity of the SOI layer is unsatisfactory.
The present applicant has disclosed a new SOI technique in Japanese Patent Laid-Open No. 5-21338. In this technique, a first substrate obtained by forming a porous layer on a single-crystal Si substrate and a non-porous single-crystal layer on its surface is bonded to a second substrate via an insulating layer. After this, the bonded substrate stack is separated into two substrates at the porous layer, thereby transferring the non-porous single-crystal layer to the second substrate. This technique is advantageous because the film thickness uniformity of the SOI layer is good, the crystal defect density in the SOI layer can be decreased, the surface planarity of the SOI layer is good, no expensive manufacturing apparatus with special specifications is required, and SOI substrates having about several hundred-xc3x85 to 10 xcexcm thick SOI films can be manufactured by a single manufacturing apparatus.
The present applicant has also disclosed, in Japanese Patent Laid-Open No. 7-302889, a technique of bonding first and second substrates, separating the first substrate from the second substrate without breaking the first substrate, smoothing the surface of the separated first substrate, forming a porous layer again, and reusing the substrate. Since the first substrate is not wasted, this technique is advantageous in largely reducing the manufacturing cost and simplifying the manufacturing process.
To separate the bonded substrate stack into two substrates without breaking the first and second substrates, the following methods are available: the two substrates are pulled in opposite directions while applying a force in a direction perpendicular to the bonding interface; a shearing force is applied parallel to the bonding interface (for example, the two substrates are moved in opposite directions in a plane parallel to the bonding interface, or the two substrates are rotated in opposite directions while applying a force in the circumferential direction); pressure is applied in a direction perpendicular to the bonding interface; a wave energy such as an ultrasonic wave is applied to the separation region; a peeling member (e.g., a sharp blade such as a knife) is inserted into the separation region parallel to the bonding interface from the side surface side of the bonded substrate stack; the expansion energy of a substance filling the pores of the porous layer functioning as the separation region is used; the porous layer functioning as the separation region is thermally oxidized from the side surface of the bonded substrate stack to expand the volume of the porous layer and separate the substrates; and the porous layer functioning as the separation region is selectively etched from the side surface of the bonded substrate stack to separate the substrates.
Porous Si was found in 1956 by Uhlir et al. who were studying electropolishing of semiconductors (A. Uhlir, Bell Syst. Tech. J., vol. 35, 333 (1956)). Porous Si can be formed by anodizing an Si substrate in an HF solution.
Unagami et al. studied the dissolution reaction of Si upon anodizing and reported that holes were necessary for anodizing reaction of Si in an HF solution, and the reaction was as follows (T. Unagami, J. Electrochem. Soc., vol. 127, 476 (1980)).
Si+2HF+(2xe2x88x92n)e+xe2x86x92SiF2+2H++nexe2x88x92
SiF2+2HFxe2x86x92SiF4+H2
SiF4+2HFxe2x86x92H2SiF6
or
Si+4HF+(4xe2x88x92xcex)e+xe2x86x92SiF4+4H++xcexexe2x88x92
SiF4+2HFxe2x86x92H2SiF6
where e+ and exe2x88x92 represent a hole and an electron, respectively, and n and xcex are the number of holes necessary to dissolve one Si atom. According to them, when n greater than 2 or xcex greater than 4, porous Si is formed.
The above fact suggests that p-type Si having holes is converted into porous Si while n-type Si is not converted. The selectivity in this conversion has been reported by Nagano et al. and Imai (Nagano, Nakajima, Anno, Onaka, and Kajiwara, IEICE Technical Report, vol. 79, SSD79-9549 (1979)), (K. Imai, Solid-State Electronics, vol. 24, 159 (1981)).
However, it has also been reported that n-type at a high concentration is converted into porous Si (R. P. Holmstrom and J. Y. Chi, Appl. Phys. Lett., vol. 42, 386 (1983)). Hence, it is important to select a substrate which can be converted into a porous Si substrate independently of p- or n-type.
To form a porous layer, instead of the above anodizing method, for example, a method of implanting ions into a silicon substrate may also be used.
For example, in the method described in Japanese Patent Laid-Open No. 5-21338, i.e., the method of preparing a substrate (to be referred to as a bonded substrate stack hereinafter) by bonding a first substrate having a non-porous layer such as a single-crystal Si layer on a porous layer to a second substrate via an insulating layer, and separating the bonded substrate stack at the porous layer so as to transfer the non-porous layer formed on the first substrate side to the second substrate, the technique of separating the bonded substrate stack is very important.
For example, in separating the bonded substrate stack, if the bonded substrate stack is separated at a portion other than the porous layer serving as a separation layer, for example, the non-porous layer (e.g., a single-crystal Si layer) to be used as an active layer breaks, and no desired SOI substrate is obtained.
The present invention has been made in consideration of the above situation, and has as its object to appropriately separate a composite member such as a bonded substrate stack at a separation layer such as a porous layer.
A processing method according to the first aspect of the present invention relates to a method of separating a composite member having a structure in which a first member having a separation layer inside is brought into tight contact with a second member. The composite member has a projecting portion at which a peripheral edge of the first member projects outside a peripheral edge of the second member. The processing method comprises the detection step of detecting the projecting portion of the composite member, and the separation step of starting separating the composite member from the projecting portion detected in the detection step and then separating the composite member into two members at the separation layer.
The composite member preferably has a structure in which the first and second members are brought into tight contact with each other while shifting central positions.
The separation step preferably comprises, e.g., the pre-separation step of forming a separation start portion by processing the projecting portion, and the main separation step of starting separating the composite member from the separation start portion and then substantially breaking only the separation layer to separate the composite member into two members at the separation layer.
In the detection step, the projecting portion is detected using, e.g., a noncontact or contact sensor.
In the detection step, the projecting portion can be detected using, e.g., a sensor arranged on a side of a peripheral edge of the composite member.
In the detection step, the projecting portion can be detected using, e.g., a sensor arranged at a position opposing a bonding interface between the first and second members.
In the detection step, the projecting portion can be detected by, e.g., detecting a shift amount between the peripheral edge of the first member and the peripheral edge of the second member along an outer periphery of the composite member.
In the detection step, the projecting portion can be detected by, e.g., sensing the composite member with an image sensing device and processing a sensed image.
In the detection step, the projecting portion can be detected by, e.g., sensing the composite member with an image sensing device while illuminating the composite member so as to form a shadow at the projecting portion, and processing a sensed image.
In the detection step, the projecting portion can be detected by, e.g., sensing a peripheral edge of the composite member with an image sensing device arranged in a tangent direction and processing a sensed image.
This separating method preferably further comprises the arrangement step of, before execution of the separation step, arranging the composite member to make the projecting portion detected in the detection step match a work position in the separation step.
In the detection step, preferably, a portion where the peripheral edge of the first member most largely projects is detected as the projecting portion.
According to the second aspect of the present invention, there is provided a thin film manufacturing method including the step of transferring a transfer layer on a surface of a first member to a second member, comprising the preparation step of bringing the first member having a separation layer inside and the transfer layer on the separation layer into tight contact with the second member to prepare a composite member having a projecting portion at which a peripheral edge of the first member projects outside a peripheral edge of the second member, the detection step of detecting the projecting portion of the composite member, and the separation step of starting separating the composite member from the projecting portion detected in the detection step and then separating the composite member into two members at the separation layer, thereby transferring the transfer layer of the first member to the second member.
A processing method according to the third aspect of the present invention relates to a separating method of separating a bonded substrate stack, which has a structure in which a transfer layer of a first substrate having a separation layer inside and the transfer layer on the separation layer is brought into tight contact with a second substrate, into two substrates. The bonded substrate stack has a projecting portion at which a peripheral edge of the first substrate projects outside a peripheral edge of the second substrate. The separating method comprises the detection step of detecting the projecting portion of the bonded substrate stack, and the separation step of starting separating the bonded substrate stack from the projecting portion detected in the detection step and then separating the bonded substrate stack into two substrates at the separation layer.
Preferably, the first and second substrates have the same size, and the bonded substrate stack has a structure in which the first and second substrates are brought into tight contact with each other while shifting central positions.
The separation step preferably comprises the pre-separation step of forming a separation start portion by processing the projecting portion, and the main separation step of starting separating the bonded substrate stack from the separation start portion and then substantially breaking only the separation layer to separate the bonded substrate stack into two substrates at the separation layer.
In the detection step, the projecting portion can be detected using, e.g., a noncontact or contact sensor.
In the detection step, the projecting portion can be detected using, e.g., a sensor arranged on a side of a peripheral edge of the bonded substrate stack.
In the detection step, the projecting portion can be detected using, e.g., a sensor arranged at a position opposing a bonding interface between the first and second substrates.
In the detection step, the projecting portion can be detected by, e.g., detecting a shift amount between the peripheral edge of the first substrate and the peripheral edge of the second substrate along an outer periphery of the bonded substrate stack.
In the detection step, the projecting portion can be detected by, e.g., sensing the bonded substrate stack with an image sensing device and processing a sensed image.
In the detection step, the projecting portion can be detected by, e.g., sensing the bonded substrate stack with an image sensing device while illuminating the bonded substrate stack so as to form a shadow at the projecting portion, and processing a signal of a sensed image.
In the detection step, the projecting portion can be detected by, e.g., sensing a peripheral edge of the bonded substrate stack with an image sensing device arranged in a tangent direction and processing a signal of a sensed image.
This processing method preferably further comprises the arrangement step of, before execution of the separation step, arranging the bonded substrate stack to make the projecting portion detected in the detection step match a work position in the separation step.
In the detection step, preferably, a portion where the peripheral edge of the first substrate most largely projects is detected as the projecting portion.
According to the fourth aspect of the present invention, there is provided a thin film manufacturing method including the step of transferring a transfer layer on a surface of a first substrate to a second substrate, comprising the preparation step of bonding the transfer layer of the first substrate having a separation layer inside and the transfer layer on the separation layer to the second substrate to prepare a bonded substrate stack having a projecting portion at which a peripheral edge of the first substrate projects outside a peripheral edge of the second substrate, the detection step of detecting the projecting portion of the bonded substrate stack, and the separation step of starting separating the bonded substrate stack from the projecting portion detected in the detection step and then separating the bonded substrate stack at the separation layer, thereby transferring the transfer layer of the first substrate to the second substrate.
According to the fifth aspect of the present invention, there is provided a thin film manufacturing method comprising the preparation step of bonding a surface of a first substrate having a separation layer inside and a transfer layer on the separation layer to a second substrate to prepare a bonded substrate stack having a projecting portion at which a peripheral edge of the first substrate projects outside a peripheral edge of the second substrate, the detection step of detecting the projecting portion of the bonded substrate stack, and the separation step of starting separating the bonded substrate stack from the projecting portion detected in the detection step and then separating the bonded substrate stack at the separation layer, thereby transferring the transfer layer of the first substrate to the second substrate.
The transfer layer includes, e.g., a single-crystal Si layer. The transfer layer may have not only the single-crystal Si layer but also an insulating layer on the single-crystal Si layer.
In the preparation step, for example, the first and second substrates having the same size are preferably brought into tight contact with each other while shifting central positions to prepare the bonded substrate stack.
The separation step preferably comprises the pre-separation step of forming a separation start portion by processing the projecting portion, and the main separation step of starting separating the bonded substrate stack from the separation start portion and then substantially breaking only the separation layer to separate the bonded substrate stack into two substrates at the separation layer.
In the pre-separation step, the separation start portion can be formed by, e.g., injecting a fluid to the projecting portion.
In the pre-separation step, the separation start portion can be formed by, e.g., inserting a wedge-shaped member to a gap between the first substrate and the second substrate at the projecting portion.
In the separation step, the separation start portion can be formed on the bonded substrate stack by injecting a fluid to the projecting portion, and then, separation of the bonded substrate stack can be continued while changing a position to which the fluid is injected.
In the separation step, the bonded substrate stack can be separated by, e.g., inserting a wedge-shaped member to a gap between the first substrate and the second substrate at the projecting portion.
The separation start portion is, e.g., a portion at which the separation layer has a most fragile structure.
The separation start portion is, e.g., a portion at which the transfer layer is removed and the separation layer under the transfer layer is exposed.
At the separation start portion, for example, the separation layer is exposed and a peripheral edge of the separation layer has a recess inward of the bonded substrate stack.
In the detection step, the projecting portion is detected using, e.g., a noncontact or contact sensor.
In the detection step, the projecting portion can be detected using, e.g., a sensor arranged on a side of a peripheral edge of the bonded substrate stack.
In the detection step, the projecting portion can be detected using, e.g., a sensor arranged at a position opposing a bonding interface between the first and second substrates.
In the detection step, the projecting portion can be detected by, e.g., detecting a shift amount between the peripheral edge of the first substrate and the peripheral edge of the second substrate along an outer periphery of the bonded substrate stack.
In the detection step, the projecting portion can be detected by, e.g., sensing the bonded substrate stack with an image sensing device and processing a signal of a sensed image.
In the detection step, the projecting portion can be detected by, e.g., sensing the bonded substrate stack with an image sensing device while illuminating the bonded substrate stack so as to form a shadow at the projecting portion, and processing a signal of a sensed image.
In the detection step, the projecting portion can be detected by, e.g., sensing a peripheral edge of the bonded substrate stack with an image sensing device arranged in a tangent direction and processing a signal of a sensed image.
The substrate manufacturing method preferably further comprises the arrangement step of, before execution of the separation step, arranging the bonded substrate stack to make the projecting portion detected in the detection step match a work position in the separation step.
In the detection step, preferably, a portion where the peripheral edge of the first substrate most largely projects is detected as the projecting portion.
A detection method according to the sixth aspect of the present invention relates to a detection method of detecting a feature portion of a composite member having a structure in which a first member having a separation layer inside is brought into tight contact with a second member. The composite member has, as the feature portion, a portion at which a peripheral edge of the first member projects outside a peripheral edge of the second member. The detection method comprises the shift detection step of detecting a shift between the peripheral edge of the first member and the peripheral edge of the second member along an outer periphery of the composite member, and the determination step of determining the feature portion on the basis of a detection result in the shift detection step.
In the shift detection step, for example, the shift between the peripheral edge of the first member and the peripheral edge of the second member is preferably detected along a perimeter of the composite member.
In the shift detection step, the shift is detected using, e.g., a noncontact or contact sensor.
In the shift detection step, the shift can be detected using, e.g., a sensor arranged on a side of a peripheral edge of the composite member.
In the shift detection step, the shift can be detected using, e.g., a sensor arranged at a position opposing a bonding interface between the first and second members.
In the shift detection step, the shift can be detected by, e.g., sensing the composite member with an image sensing device and processing a signal of a sensed image.
In the shift detection step, the shift can be detected by, e.g., sensing the composite member with an image sensing device while illuminating the composite member so as to form a shadow at the projecting portion, and processing a sensed image.
In the shift detection step, the shift can be detected by, e.g., sensing a peripheral edge of the composite member with an image sensing device arranged in a tangent direction and processing a sensed image.
In the determination step, preferably, a portion where the peripheral edge of the first member most largely projects is determined as the feature portion.
A processing method according to the seventh aspect of the present invention relates to a processing method of positioning, to a predetermined position, a feature portion of a composite member having a structure in which a first member having a separation layer inside is brought into tight contact with a second member. The composite member has, as the feature portion, a portion at which a peripheral edge of the first member projects outside a peripheral edge of the second member. The processing method comprises the shift detection step of detecting a shift between the peripheral edge of the first member and the peripheral edge of the second member along an outer periphery of the composite member, the determination step of determining the feature portion on the basis of a detection result in the shift detection step, and the arrangement step of arranging the composite member to make the feature portion determined in the determination step match the predetermined position.
A detection apparatus according to the eighth aspect of the present invention relates to a detection apparatus for detecting a feature portion of a composite member having a structure in which a first member having a separation layer inside is brought into tight contact with a second member. The composite member has, as the feature portion, a portion at which a peripheral edge of the first member projects outside a peripheral edge of the second member. The detection apparatus comprises shift detection means for detecting a shift between the peripheral edge of the first member and the peripheral edge of the second member along an outer periphery of the composite member, and determination means for determining the feature portion on the basis of a detection result by the shift detection means.
The shift detection means preferably detects the shift between the peripheral edge of the first member and the peripheral edge of the second member along a perimeter of the composite member.
The shift detection means detects the shift using, e.g., a noncontact or contact sensor.
The shift detection means has, e.g., a sensor arranged on a side of a peripheral edge of the composite member and can detect the shift using the sensor.
The shift detection means has, e.g., a sensor arranged at a position opposing a bonding interface between the first and second members and can detect the shift using the sensor.
The shift detection means has, e.g., an image sensing device and can detect the shift by sensing the composite member and processing a sensed image.
The shift detection means has, e.g., an illumination device and an image sensing device and can detect the shift by sensing the composite member with the image sensing device while illuminating the composite member with the illumination device so as to form a shadow at the projecting portion, and processing a sensed image.
The shift detection means has, e.g., an image sensing device arranged in a tangent direction of a peripheral edge of the composite member and can detect the shift by sensing the peripheral edge of the composite member with the image sensing device and processing a sensed image.
The determination means preferably determines, as the feature portion, a portion where the peripheral edge of the first member most largely projects.
A positioning apparatus according to the ninth aspect of the present invention relates to a positioning apparatus for positioning, to a predetermined position, a feature portion of a composite member having a structure in which a first member having a separation layer inside is brought into tight contact with a second member. The composite member has, as the feature portion, a portion at which a peripheral edge of the first member projects outside a peripheral edge of the second member, The positioning apparatus comprises shift detection means for detecting a shift between the peripheral edge of the first member and the peripheral edge of the second member along an outer periphery of the composite member, determination means for determining the feature portion on the basis of a detection result by the shift detection means, and arrangement means for arranging the composite member to make the feature portion determined by the determination means match the predetermined position.
A processing apparatus according to the tenth aspect of the present invention comprises a positioning apparatus for positioning a feature portion of a composite member having a structure in which a first member having a separation layer inside is brought into tight contact with a second member, and a processing device for processing the composite member at a work position. In the processing apparatus, the composite member has, as the feature portion, a portion at which a peripheral edge of the second member, and the positioning apparatus positions the feature portion of the composite member to the work position of the processing apparatus.
The processing device preferably comprises a separating apparatus for starting separating the composite member from the feature portion and then separating the composite member into two members at the separation layer.
A semiconductor device manufacturing method according to the eleventh aspect of the present invention comprises the steps of preparing an SOI substrate made using the thin film manufacturing method according to the fifth aspect of the present invention, and element-isolating an SOI layer of the SOI substrate so as to form a transistor on the element-isolated SOI layer.
The transistor is, e.g., a partial depletion type FET or a complete depletion type FET.
A semiconductor device according to the twelfth aspect of the present invention can be manufactured by the semiconductor device manufacturing method according to the eleventh aspect of the invention.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.